/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
 var countNodes = function(root) {
    if(root === null) return 0
    let leftHeight = 0
    let rightHeight = 0
    let left = root.left
    let right = root.right
    while(left.left){
      leftHeight++
    }
    while(right.right){
      rightHeight++
    }
    if(leftHeight === rightHeight){
      return Math.pow(2,leftHeight)+1
    }
    return countNodes(root.left) + countNodes(node.right) + 1
};